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  <div class="question_difficulty">
   难度：Hard
  </div>
  <div>
   <h1 class="question_title">
    282. Expression Add Operators
   </h1>
   <p>
    Given a string that contains only digits
    <code>
     0-9
    </code>
    and a target value, return all possibilities to add
    <b>
     binary
    </b>
    operators (not unary)
    <code>
     +
    </code>
    ,
    <code>
     -
    </code>
    , or
    <code>
     *
    </code>
    between the digits so they evaluate to the target value.
   </p>
   <p>
    <b>
     Example 1:
    </b>
   </p>
   <pre>
<b>Input:</b> <code><em>num</em> = </code>"123", <em>target</em> = 6
<b>Output: </b>["1+2+3", "1*2*3"] 
</pre>
   <p>
    <b>
     Example 2:
    </b>
   </p>
   <pre>
<b>Input:</b> <code><em>num</em> = </code>"232", <em>target</em> = 8
<b>Output: </b>["2*3+2", "2+3*2"]</pre>
   <p>
    <b>
     Example 3:
    </b>
   </p>
   <pre>
<b>Input:</b> <code><em>num</em> = </code>"105", <em>target</em> = 5
<b>Output: </b>["1*0+5","10-5"]</pre>
   <p>
    <b>
     Example 4:
    </b>
   </p>
   <pre>
<b>Input:</b> <code><em>num</em> = </code>"00", <em>target</em> = 0
<b>Output: </b>["0+0", "0-0", "0*0"]
</pre>
   <p>
    <b>
     Example 5:
    </b>
   </p>
   <pre>
<b>Input:</b> <code><em>num</em> = </code>"3456237490", <em>target</em> = 9191
<b>Output: </b>[]
</pre>
  </div>
  <div>
   <h1 class="question_title">
    282. 给表达式添加运算符
   </h1>
   <p>
    给定一个仅包含数字&nbsp;
    <code>
     0-9
    </code>
    &nbsp;的字符串和一个目标值，在数字之间添加
    <strong>
     二元
    </strong>
    运算符（不是一元）
    <code>
     +
    </code>
    、
    <code>
     -
    </code>
    &nbsp;或&nbsp;
    <code>
     *
    </code>
    &nbsp;，返回所有能够得到目标值的表达式。
   </p>
   <p>
    <strong>
     示例 1:
    </strong>
   </p>
   <pre><strong>输入:</strong> <code><em>num</em> = </code>"123", <em>target</em> = 6
<strong>输出: </strong>["1+2+3", "1*2*3"] 
</pre>
   <p>
    <strong>
     示例&nbsp;2:
    </strong>
   </p>
   <pre><strong>输入:</strong> <code><em>num</em> = </code>"232", <em>target</em> = 8
<strong>输出: </strong>["2*3+2", "2+3*2"]</pre>
   <p>
    <strong>
     示例 3:
    </strong>
   </p>
   <pre><strong>输入:</strong> <code><em>num</em> = </code>"105", <em>target</em> = 5
<strong>输出: </strong>["1*0+5","10-5"]</pre>
   <p>
    <strong>
     示例&nbsp;4:
    </strong>
   </p>
   <pre><strong>输入:</strong> <code><em>num</em> = </code>"00", <em>target</em> = 0
<strong>输出: </strong>["0+0", "0-0", "0*0"]
</pre>
   <p>
    <strong>
     示例 5:
    </strong>
   </p>
   <pre><strong>输入:</strong> <code><em>num</em> = </code>"3456237490", <em>target</em> = 9191
<strong>输出: </strong>[]
</pre>
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